Basic magnesium sulfate [MgSO4.5Mg(OH)2.3H2O] can be utilized as wastewater-processing material. This utilization is disclosed in the following published documents.
JP 6-226017A discloses a method for removing fine particles and oil from wastewater by means of basic magnesium sulfate granules which comprise granulated plural fibrous basic magnesium sulfate particles. This publication describes a method comprising bringing wastewater containing fine particles and oil into contact with basic magnesium sulfate granules to produce aggregated masses and removing the aggregated masses from the wastewater by filtering for the fine particle-aggregated masses and by floating the oil-agglomerated masses.
JP 2005-231927A discloses basic magnesium sulfate granules comprising agglomerated composition comprising plural fibrous basic magnesium sulfate particles which are bonded to each other by a fibrous inorganic compound such as xonotolite or sepiolite or a fibrillated polytetrafluoroethylene. The basic magnesium sulfate granules are stated to be valuable as wastewater-processing material because the basic magnesium sulfate granules show improved structural stability, as compared with basic magnesium sulfate granules having no binding material. This publication further describes that the basic magnesium sulfate can be used for removing silica and lead by way of adsorption.
JP 2003-47972A describes a method of removing fluorine from wastewater discharged from desulfurization apparatuses which comprises employing magnesium sulfate as the absorbent in the desulfurization apparatus and adding sodium hydroxide to the wastewater discharged the desulfurization apparatus, thereby producing fluorine-absorbed basic magnesium sulfate and magnesium hydroxide.
As is described above, the granules composed of fibrous basic magnesium sulfate particles are valuable as wastewater-processing material because the granules can cause aggregation of fine particles and oil in wastewater and removing heavy metals and fluorine by way of adsorption. The basic magnesium sulfate granules for the use as wastewater-processing material preferably show appropriate characteristics such as a low bulk density that means presence of vacant space within the granules so that water easily enter the vacant space of the granules; and a high strength that means a high structural stability in water so that the granules are resistant to deintegration which results in dispersion of fibrous particles in running water.
As a result of studies, the present inventors have noted that the known basic magnesium sulfate granules do not show high strength enough for the employment as wastewater-processing material and that the granules should have increased strength.